Battery banks loosing voltage while being charged

[Kiss My Aft]

Hey, I have a Xantrex Inverter Charger on a Beneteau 46 (TT, Tropic Thunder). House batteries are new Gel (less than 6 months). Engine batteries are AGM (less than a year). Recently, the main buss alarm is going off when the engine is started; first time was a month ago; every other time I took TT out. Now it is every time the boat is started. In talking to Beneteau, they state that is a common problem due to the fact that the alarm is set to go off if there is more than a 0.3 V drop in the battery charge; there is no way to adjust the sensitivity of the alarm. They suggest to rev the engine and it should go away. I have had the alternator on the engine checked out at it is at or better than manufacture specs. The Xantrex system is showing that the house bank of batteries are at 100% and I have tested the engine bank and they are also at or near 100%. Seemingly, the batteries come back to dock fully charged when under power by the alternator on the engine . . . but when using shore power, the batteries come up to voltage but over time start loosing voltage. This is one of those difficult problems to track down. Is it a leak/short in the system or is the Xantrex system starting to fail? Has anyone else had this problem? Any suggestions?

[GordMay]

Greetings and welcome aboard the CF, k m a.

[Andina Marie]

Originally Posted by Kiss My Aft

Hey, I have a Xantrex Inverter Charger on a Beneteau 46 (TT, Tropic Thunder). House batteries are new Gel (less than 6 months). Engine batteries are AGM (less than a year). Recently, the main buss alarm is going off when the engine is started; first time was a month ago; every other time I took TT out. Now it is every time the boat is started. In talking to Beneteau, they state that is a common problem due to the fact that the alarm is set to go off if there is more than a 0.3 V drop in the battery charge; there is no way to adjust the sensitivity of the alarm. They suggest to rev the engine and it should go away. I have had the alternator on the engine checked out at it is at or better than manufacture specs. The Xantrex system is showing that the house bank of batteries are at 100% and I have tested the engine bank and they are also at or near 100%. Seemingly, the batteries come back to dock fully charged when under power by the alternator on the engine . . . but when using shore power, the batteries come up to voltage but over time start loosing voltage. This is one of those difficult problems to track down. Is it a leak/short in the system or is the Xantrex system starting to fail? Has anyone else had this problem? Any suggestions?

I'm not directly familiar with the alarm but 0.3 volts trip level does not seem high enough even for new batteries when hit with engine starting loads.

However one thing to check is where the alarm is measuring the voltage. The measuring connection should be an independent wire going directly to the battery post. If it is connected to the battery positive through other cables or connections it may be seeing voltage drop in the wiring in addition to the battery.

[Terra Nova]

Disconnect the alarm or its buzzer.

[Auger01]

The symptoms you describe may be normal. Initially the xantrex will bulk charge the batteries at a higher voltage, then it will go in to the "float" mode which maintains the batteries at a lower voltage. IIRC the float voltage for gel batteries is around 13.2 volts.

[Sailor Doug]

I have had problems with Xantrex chargers. Use a good digital voltmeter to check charge voltage. I had two of the that where dropping from 14.5 voltage to 13.2 before the batteries where charged. Xantrex replaced both under warranty I ended up with damaged house bank.